Hard magnet stabilized shield for double (2DMR) or triple (3DMR) dimension magnetic reader structures

ABSTRACT

A hard magnet stabilization scheme is disclosed for a top shield and junction shields for double or triple dimension magnetic reader structures. In one design, the hard magnet (HM) adjoins a top or bottom surface of all or part of a shield domain such that the HM is recessed from the air bearing surface to satisfy reader-to-reader spacing requirements and stabilizes a closed loop magnetization in the top shield. The HM may have a height and width greater than that of the top shield. The top shield may have a ring shape with a HM formed above, below, or within the ring shape, and wherein the HM stabilizes a vortex magnetization. HM magnetization is set or reset from room temperature to 100° C. to maintain a desired magnetization direction in the top shield, junction shield, and free layer in the sensor.

This is a Divisional application of U.S. patent application Ser. No.15/357,070, filed on Nov. 21, 2016, and issued as U.S. Pat. No.10,115,418, which is herein incorporated by reference in its entirety,and assigned to a common assignee.

RELATED PATENT APPLICATIONS

This application is related to the following: U.S. Pat. Nos. 8,369,048;8,514,524, 8,824,106, U.S. patent application Ser. No. 14/848,376, filedon Sep. 9, 2015; and U.S. Pat. No. 9,230,577; assigned to a commonassignee and herein incorporated by reference in their entirety.

TECHNICAL FIELD

The present disclosure relates to a stabilization scheme for shieldsbetween readers in 2DMR and 3DMR designs, and in particular to a hardmagnet layer that stabilizes an overlying or underlying shield throughexchange coupling thereby making the shield less susceptible tomagnetization flipping to an incorrect state.

BACKGROUND

In a magnetic recording device in which a read head comprises amagnetoresistive (MR) sensor, there is a constant drive to increaserecording density. One trend used in the industry to achieve thisobjective is to decrease the size of the MR sensor. Typically, thesensor stack has two ferromagnetic layers that are separated by anon-magnetic layer. One of the ferromagnetic layers is a reference orpinned layer wherein the magnetization direction is fixed by exchangecoupling with an adjacent antiferromagnetic (AFM) pinning layer. Thesecond ferromagnetic layer is a free layer with a magnetization thatrotates in response to external magnetic fields, and is aligned eitherparallel or anti-parallel to the magnetization in the pinned layer toestablish a “0” or “1” memory state. When an external magnetic field isapplied by passing the MR sensor over a recording medium at an airbearing surface (ABS), the free layer magnetic moment may rotate to anopposite direction. A MR sensor may be based on a tunnelingmagnetoresistive effect where the two ferromagnetic layers are separatedby a thin non-magnetic dielectric layer. A sense current is used todetect a resistance value which is lower in a “0” memory state than in a“1” memory state. In a CPP configuration, a sense current is passed froma top shield through the sensor layers to a bottom shield in aperpendicular-to-plane direction.

In a longitudinal biasing read head design, hard bias films of highcoercivity are abutted against the edges of the sensor and particularlyagainst the sides of the free layer. In other designs, there is a thinseed layer between the hard bias layer and free layer. By arranging forthe flux flow in the free layer to be equal to the flux flow in theadjoining hard bias layer, the demagnetizing field at the junction edgesof the aforementioned layers vanishes because of the absence of magneticpoles at the junction. As the critical dimensions for sensor elementsbecome smaller with higher recording density requirements, the freelayer becomes more volatile and more difficult to bias. Traditionalbiasing schemes using a hard magnet bias have become problematic due torandomly distributed hard magnetic grains within the hard bias layer.

In recent years, 2DMR and 3DMR configurations have become attractivefrom an areal density improvement standpoint. However, shield stabilityis more difficult to control in 2DMR and 3DMR schemes because of arequirement to shrink reader-to-reader spacing (RRS) and in view ofrepeated thermal treatments during fabrication that can readily flip themagnetization in the shields. Although an upper shield that isstabilized through antiferromagnetic (AFM) coupling provides goodthermal stability in a single reader (1DMR) structure, repeated heattreatments on shields in a 2DMR or 3DMR process flow greatly increaseshield instability and flip rate. In addition, shields that arestabilized with exchange coupling become less stable due to the reducedRRS requirement. Since top and bottom shields are commonly directlycoupled or anti-ferromagnetically coupled to the junction shield thatbiases a free layer in the MR sensor, shield instability will directlytranslate into reader instability and will adversely impact signal tonoise ratio (SNR) and bit error rate (BER). Accordingly, a new read headstructure is needed wherein shield stability is improved in 2DMR and3DMR configurations while maintaining acceptable SNR and BER.

SUMMARY

One objective of the present disclosure is to provide a stabilizationscheme for a top shield in a MR sensor structure that also providesimproved stability to a free layer in the MR sensor.

A second objective of the present disclosure is to provide astabilization scheme according to the first objective that is compatiblewith reduced reader-to-reader spacing (RRS) requirements.

According to one embodiment of the present disclosure, these objectivesare achieved by including a hard magnet (HM) layer that is recessed fromthe ABS and is coupled with one of the domains in a top shield.Preferably, the HM layer adjoins a portion of the bottom surface of thetop shield to enable reduced RRS. However, in some embodiments, the hardmagnet layer may adjoin a top surface of the top shield. In anotherembodiment, the HM layer is embedded in the top shield by directlyreplacing part or all of a magnetic domain. An advantage ofincorporating a HM layer in a read head design as described herein isthat the HM magnetization is easily set or reset at room temperature.Moreover, HM coupling to the top shield maintains the top shieldmagnetization in the correct direction. If an annealing process duringreader fabrication inadvertently flips the top shield magnetization toan undesired direction, resetting the HM layer magnetization does notrequire an additional high temperature anneal to reset the top shieldmagnetization because the top shield reset will occur as a result ofcoupling to a reset HM layer.

The MR sensor includes a free layer formed in a plane that is orthogonalto the ABS and with a magnetic moment in a direction parallel to theABS. The MR sensor has a bottom surface formed on a bottom shield, a topsurface that adjoins the top shield, and sidewalls connecting the topand bottom surfaces. There is a non-magnetic insulation layer adjoiningthe sidewalls of the MR sensor and a second section thereof that extendsalong a top surface of the bottom shield. The second section ofinsulation layer is formed in a plane that is parallel to the planes ofthe sensor layers and serves as a substrate for side shields (junctionshields) that are preferably comprised of a single ferromagnetic layer.

From a top-down view, the top shield has a cross-track width (w), and aheight (h) orthogonal to the ABS that are substantially greater than thecross-track width and height dimensions, respectively, of the MR sensor.According to one embodiment where the top shield has a rectangularshape, magnetization in the top shield forms a closed loop or enclosedstate. Magnetization has a first (cross-track) direction in a firstportion (domain) at the ABS, a second direction orthogonal to the ABS ina second domain proximate to a first top shield side, a third directionopposite to the first direction in a third domain at a top shieldbackside, and a fourth direction opposite to the second direction in afourth domain proximate to a second top shield side. In one aspect, thefirst domain extends orthogonal from the ABS to a height (½ h) at abackside center section thereof, and the third domain extends from thebackside center section of the first domain to height h.

The first and third domains may have a substantially trapezoidal shape.In various embodiments, a HM layer has a shape substantially equivalentto that of the third domain, and contacts a top or bottom surface of thetop shield third domain or is formed within the top shield. Thus, HMmagnetization is set in the third direction and maintains magnetizationin the top shield third domain in the third direction. Since the topshield has a closed loop magnetization, magnetization in the other topshield domains is maintained in the desired direction by influence fromthe third top shield domain thereby establishing top shield magneticstability.

According to another embodiment, the top shield has two rectangularshaped domains that are adjoined along a side aligned parallel to theABS. A front domain has a magnetization that is parallel to the ABS inthe first direction, and a back domain has a magnetization that isopposite to the first direction. Each of the front and back domains havea cross-track width “w”, and the back domain has a backside at height“h” from the ABS. The HM layer preferably adjoins a bottom surface ofthe top shield back domain and has a cross-track width greater than “w”,and a height that extends more than ½ h from a front side to a backsidethat is at a height greater than “h” from the ABS to avoid edgemagnetostatic coupling. The HM layer front side is recessed a distanceof about “½ h” from the ABS.

In an alternative embodiment, the top shield has a shape substantiallyin the form of a ring with an inner diameter “d” filled with anisolation material, and radius “r” between and an inner side and outerside from a top-down view. A front side of the ring abuts the ABS abovethe MR sensor. Magnetization within the ring has a stable vortex statewith a clockwise or counterclockwise direction. Preferably, there is aHM layer having a rectangular or trapezoidal shape, for example, whichadjoins a portion of top shield bottom surface. Magnetization within theHM layer is set or reset in a direction that maintains the desiredclockwise or counterclockwise magnetization in the top shield ringshape.

In another embodiment that features a fully coupled top shield design, aHM layer having a substantially rectangular shape adjoins essentiallyall of the top shield bottom surface except in a region over the MRsensor and junction shields that adjoin the MR sensor sidewalls. The HMlayer has a thickness equivalent to that of the MR sensor and junctionshields at the ABS, and extends in a cross-track direction from an outerside of each junction shield to a far side of the read head structure.In a 2DMR layout, an isolation layer is formed between a first topshield that is above a first MR sensor, and a second bottom shield thatis below a second MR sensor.

For a 3DMR structure, a first HM layer may be employed to stabilize afirst top shield on a bottommost MR sensor, a second HM layer stabilizesa second top shield in a middle MR sensor, and a third HM layer may ormay not be used to stabilize a third top shield on the uppermost MRsensor in the sensor stack.

The present disclosure also includes a method involving a sequence ofprocess steps of forming a HM layer in the fully coupled top shielddesign.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an ABS view showing a MR sensor formed between top and bottomshields, and stabilized side shields with antiferromagnetic coupling areused to longitudinally bias a free layer according to a prior artdesign.

FIG. 2 shows an ABS view of a 2DMR read head structure that includes twoMR sensors each having junction shields and a hard magnet layer formedaccording to an embodiment of the present disclosure.

FIGS. 3A-3B are top-down views of the top shields in the 2DMR structureof FIG. 2 wherein a magnetic domain adjoins a surface of a hard magnetlayer for magnetization stabilization according to an embodiment of thepresent disclosure.

FIGS. 4A-4B are top-down views of the top shields in the 2DMR structureof FIG. 2 wherein a magnetic domain is replaced by a hard magnet layerfor magnetic stabilization according to another embodiment of thepresent disclosure.

FIG. 5A shows a top-down view and FIG. 5B depicts a cross-sectional viewwherein the HM layer in FIG. 3A is shifted from above a top shielddomain to below the top shield domain according to another embodiment ofthe present disclosure.

FIGS. 6A-6B are top-down views of the top shields in the 2DMR structureof FIG. 2 wherein a top shield magnetic domain adjoins a top surface ofa hard magnet layer that has a greater cross-track width and height thanthe magnetic domain according to another embodiment of the presentdisclosure.

FIG. 7 is a top-down view of a top shield with a circular shape that isstabilized by coupling with a hard magnet layer according to anembodiment of the present disclosure.

FIGS. 8A-8B are top-down views of hard magnetic layers that are eachused to stabilize an overlying top shield in a fully coupled scheme in a2DMR structure according to an embodiment of the present disclosure.

FIG. 9 is an ABS view of a hard magnet layer that is coupled to anoverlying top shield in a 1DMR structure having a MR sensor and junctionshields according to another embodiment of the present disclosure.

FIG. 10 is an ABS view of another embodiment of the present disclosurewherein the hard magnet layers in FIGS. 8A-8B are incorporated in a 2DMRstructure.

FIGS. 11-15 are ABS views that show a series of steps used to fabricatethe read head structure in FIG. 9.

FIG. 16 is an ABS view of a 3DMR structure wherein one or more topshields are stabilized by a HM layer according to an embodiment of thepresent disclosure.

DETAILED DESCRIPTION

The present disclosure is a stabilized shield design for a magnetic readhead wherein a hard magnet layer with a magnetization that is set orreset around room temperature is coupled to a top shield, for example,to preserve a closed loop magnetization therein. The stabilized shieldis responsible for maintaining a stable magnetization direction withinan adjacent junction shield that translates into improved MR sensorstability, better SNR, and reduced BER. In the drawings, the y-axis is across-track direction, the z-axis is a down-track direction, and thex-axis is in a direction orthogonal to the ABS and towards a back end ofthe read head. The stabilized shield design described herein is notlimited to a particular read head structure, and is especially effectivein 2DMR and 3DMR configurations where a plurality of thermal treatmentsare employed during fabrication. The term “front side” refers to a sideof a layer that faces the ABS or is at the ABS while “backside” is aside of the layer opposite to the front side.

Referring to FIG. 1, a portion of a read head previously fabricated bythe inventors and disclosed in related U.S. Pat. No. 9,230,577 isdepicted. The read head is formed on a substrate (not shown) that may becomprised of AlTiC (alumina+TiC). The substrate is typically part of aslider formed in an array of sliders on a wafer. After the read head orcombined read head/write head is fabricated, the wafer is sliced to formrows of sliders. Each row is typically lapped to afford an ABS beforedicing to fabricate individual sliders that are used in a magneticrecording device. Typically, the substrate has an uppermost insulationlayer made of a dielectric material such as alumina.

A bottom shield 1 also referred to as the S1 shield is formed on thesubstrate and may be comprised of NiFe, CoFe, CoFeN, or CoFeNi, or othermagnetic materials used in the art. A MR sensor having a lower layer 2d, middle free layer 2 f, and upper layer 2 h is formed on a centersection of the bottom shield. Sidewalls 2 s connect a bottom surface 2 bwith the top surface 2 t of the MR sensor. There is a non-magneticisolation layer 40 formed along the sidewalls 2 s and on portions of thebottom shield that are not covered by the MR sensor. On each side of theMR sensor, side shields 47 are stabilized through an antiferromagnetic(AFM) coupling scheme wherein a lower ferromagnetic (FM) layer 42 is AFMcoupled to middle FM layer 44 through a first AFM coupling layer 43, andthe middle FM layer is AFM coupled to a top FM layer 46 through a secondAFM coupling layer 45. Moreover, top shield 15 a is directly coupled tothe top FM layer such that magnetization 15 m 1 in the top shield isaligned in the same direction as magnetization m4 in FM layer 46.Because of AFM coupling, magnetization m2 in the lower FM layer is inthe same direction as m4 but is opposite to the m3 direction. AFMcoupling layers are made of Ru, Rh, RhRu, Re, Ir, Mo, or other metals oralloys that promote AFM coupling between FM layer 42 and FM layer 44,and between the FM layer 44 and FM layer 46, respectively. Lower FMlayer 42 is formed on seed layer 39 and is primarily responsible forproviding longitudinal biasing to free layer 2 f.

In the MR sensor of FIG. 1, layer 2 h comprises at least a cappinglayer, and layer 2 d includes a reference layer with a fixedmagnetization direction, and a non-magnetic spacer (not shown) betweenthe reference layer and free layer 2 f. Layer 2 d may also include abottommost seed layer, and an antiferromagnetic (AFM) layer such as IrMnor another Mn alloy may be formed on a side of the reference layer thatfaces away from the free layer to pin the magnetization direction in thereference layer. In other embodiments, the AFM layer (not shown) may berecessed behind the MR sensor stack or embedded in a back portion of thebottom shield 1 to satisfy reduced RRS requirements. The non-magneticspacer may be comprised of one or more metal oxides, metal oxynitrides,or metal nitrides to provide a tunneling magnetoresistive effect.

Note that the reader structure shown in FIG. 1 represents a so-called1DMR configuration. In another 1DMR design that we disclosed in relatedU.S. Pat. No. 8,369,048, the reference layer (RL) is AFM coupled to atop magnetic layer in a bottom shield, and the free layer (FL) is AFMcoupled to a bottom magnetic layer in a top shield such that RLmagnetization is anti-parallel to that of the FL in the absence of abias magnetic field or external magnetic field. Also, a hard bias layeris positioned behind the MR sensor stack to generate a bias field thatis orthogonal to the ABS.

In yet another 1DMR design that we disclosed in related U.S. Pat. No.8,514,524, the top shield is stabilized through an antiferromagnetic(AFM) coupling scheme and has an uppermost AFM layer to pin the upperferromagnetic (FM2) layer in a FM1/Ru/FM2/AFM top shield configurationwhere the Ru layer is responsible for AFM coupling between the bottomferromagnetic (FM1) layer and FM2 layer. Although all of our previousshield stabilization schemes, and especially the AFM biased top shieldafford good thermal stability in a 1 DMR layout, we have observed thatrepeated heat treatments on shields in a 2DMR or 3DMR fabricationgreatly increases shield thermal instability and magnetization fliprate. We have disclosed examples of 2DMR designs in related U.S. Pat.No. 8,824,106 and in U.S. patent application Ser. No. 14/848,376 where aconventional biasing layer is used to stabilize an adjacent free layerin each sensor element.

As disclosed in various embodiments depicted in FIGS. 3A-7, we havediscovered schemes where a hard magnet layer that is recessed behind anABS to satisfy RRS requirements is advantageously used to stabilize atop shield in one or more read heads. Although the exemplary embodimentsrefer to a 2DMR design, those skilled in the art will appreciate thatany of the HM stabilization schemes disclosed herein may also beincorporated in a 3DMR structure to stabilize one or more top shields.

An ABS view of a 2DMR structure that applies to all of the recessed HMlayer embodiments disclosed herein is illustrated in FIG. 2 where afirst reader is comprised of a first MR sensor that has layers 2 d, 2 f,2 h formed between top shield 15 and bottom shield 1 as describedpreviously. Side shields 21 are formed on either side of the first MRsensor and have a magnetization 21 m in a (+) y direction, for example,which is maintained by ferromagnetic coupling with magnetization 15 m 1in the top shield. Above top shield 15 is an isolation layer 25 thatmagnetically separates the first MR sensor from the second MR sensorcomprised of bottom layer 3 d, free layer 3 f, and upper layer 3 h wherelayers 3 d and 3 h may have the same composition and function as layers2 d and 2 h, respectively. The second MR sensor is formed between asecond bottom shield 50 and a second top shield 55. A second insulationlayer 48 adjoins the sidewalls of the second MR sensor. Side shields 31formed on the second insulation layer have a magnetization 31 m and areemployed to provide a longitudinal bias to the free layer 3 fmagnetization direction (same as 31 m). Magnetization 31 m is also inthe same direction as magnetization 55 m in the second top shieldbecause of ferromagnetic coupling. Preferably, the second MR sensor isaligned above the first MR sensor such that center plane 44 bisects eachof the aforementioned MR sensors. The center plane is orthogonal to theABS.

According to a first embodiment of the present disclosure, a top-downview of the top shield 15 in the first reader with overlying layersremoved is shown in FIG. 3A. A key feature is that a hard magnet (HM)layer 20 is formed on a top surface of a magnetic domain in top shield15. In view of reduced RRS requirements in 2DMR and 3DMR structures, theHM layer is preferably recessed behind the ABS.

In the exemplary embodiment in FIG. 3A, magnetization 20 m is set in anegative (y) direction and maintains magnetization 15 m 3 in anunderlying top shield third domain in the event of an external magneticfield disturbance. In turn, magnetization 15 m 3 maintains a closedmagnetic loop involving magnetization 15 m 1 in a positive (y) directionin a first magnetic domain 15 a having a front side 15 f at the ABS18-18, magnetization 15 m 2 in a direction orthogonal and away from theABS in a second domain 15 b with side 15 s 1, and magnetization 15 m 4in a direction orthogonal and toward the ABS in a fourth magnetic domain15 d with side 15 s 2. Magnetization 20 m may be easily set or resetfrom room temperature to about 100° C. to avoid using substantiallyhigher temperatures that may undesirably flip magnetizations 15 m 1-15 m4 in a direction opposite to their preset directions. The HM layer doesnot necessarily have a trapezoidal shape but may be a rectangle,triangle, square, or other polygon instead. Preferably, a HM layer shapeis selected that essentially matches that of the adjoining top shielddomain to provide optimum magnetic coupling thereto.

According to one aspect, the top shield has a rectangular shape withcross-track width w between sides 15 s 1 and 15 s 2, and height hbetween front side 15 f and backside 15 e. The first domain 15 a andthird domain 15 c (not shown below HM layer 20) each have a trapezoidalshape and adjoin each other at a height around ½ h from the ABS 18-18.The present disclosure also anticipates that the top shield may have asquare, trapezoidal, triangular, or another polygonal shape as long asthe magnetic domains therein form a closed loop. In the exemplaryembodiment, HM layer 20 has substantially the same trapezoidal shape asthe underlying third domain such that backside 20 b overlays on thirddomain backside 15 e, and front side 20 f is recessed about ½ h from theABS. Diagonal sides 20 s connect the front and backsides of the HMlayer. As a result, magnetic coupling is enhanced between the thirddomain and HM layer. Each of the first MR sensor 2 and second MR sensor3 have a cross-track width a and height b substantially less than w andh, respectively, in top shield 15 and second top shield 55.

Typically, the top shield 55 in the second read head is less susceptibleto magnetization flipping and does not necessarily require a HMstabilization scheme as described previously with respect to the firstread head in FIG. 3A. However, the present disclosure anticipates anembodiment where the top shield in both of the first and second readheads is stabilized by a HM layer. As depicted in FIG. 3B, the topshield in the second read head in a 2DMR design may have substantiallythe same top-down shape and properties as that of the first top shielddescribed earlier. In particular, top shield 55 has a rectangular shapewith cross-track width w between sides 55 s 1 and 55 s 2, and a height hbetween front side 55 f and back side 55 e. The first domain 55 a andthird domain 55 c (not shown below second HM layer 30) each have atrapezoidal shape and adjoin each other at a height ½ h from the ABS18-18. Moreover, the second HM layer 30 has substantially the sametrapezoidal shape as the underlying third domain such that backside 30 boverlays on the third domain backside 55 e, and front side 30 f isrecessed about ½ h from the ABS. Diagonal sides 30 s connect the frontand backsides of the HM layer.

The recessed second HM layer 30 is formed on a top surface of a domainin second top shield 55, and has magnetization 30 m that maintainsmagnetization 55 m 3 in the underlying third domain in the second topshield in the event of an external magnetic field disturbance. In turn,magnetization 55 m 3 maintains a closed magnetic loop involvingmagnetization 55 m 1 in a positive (y) direction in a first magneticdomain 55 a having a front side 55 f at the ABS 18-18, magnetization 55m 2 in a direction orthogonal and away from the ABS in a second domain55 b with side 55 s 1, and magnetization 55 m 4 in a directionorthogonal and toward the ABS in a fourth magnetic domain 55 d with side55 s 2.

Magnetic shields 1, 15, 50, 55 and junction shields 21, 31 are comprisedof CoFe, CoFeNi, CoFeN, or NiFe, for example, while HM layers 20, 30 arepreferably made of a material such as Co Pt, CoCrPt, or FePt wherein amagnetization is readily set or reset at a temperature between roomtemperature (RT) and about 100° C. Preferably, each HM layer has adown-track thickness of 100 to 200 nm when formed above the top shield(FIGS. 3A-3B) or below the top shield (FIG. 5A). Furthermore, the HMlayer is made of a material with a substantially higher magnetizationsaturation x thickness (Mst) value than the magnetic material in the topshields.

In a second embodiment illustrated in FIG. 4A, the HM layer scheme ofFIG. 3A is modified by directly replacing a magnetic domain in topshield 15 with a HM layer. In this case, HM layer 20 has a minimumthickness of around 100 nm but may have a maximum thicknesssubstantially the same as the thickness of the top shield first domain15 a, second domain 15 b, and fourth domain 15 d. The HM layer replacesthe third domain in the first top shield to form a rectangular shape ofcross-track width w and height h with the aforementioned three domains.As a result, the HM layer adjoins the first domain at front side 20 f,adjoins the second domain at a first diagonal side 20 s, and adjoins thefourth domain at a second diagonal side 20 s. Preferably, the HM layerhas a top surface that is coplanar with a top surface of the first,second, and fourth domains. Magnetization 20 m is responsible forpreventing magnetizations 15 m 1, 15 m 2, and 15 m 4 from flipping to adirection that is opposite to the preset direction thereby stabilizingthe top shield 15, side shield 21, and free layer 2 f in first MR sensorin FIG. 2.

In an alternative embodiment shown in FIG. 4B, the first read head isstabilized by HM layer 20 as previously described in FIG. 4A. Moreover,the second top shield 55 in the second read head is stabilized by asecond HM layer 30 that preferably has a top surface that is coplanarwith that of the first domain 55 a, second domain 55 b, and fourthdomain 55 d. The second HM layer replaces the third domain in the secondtop shield to form a rectangular shape of cross-track width w and heighth with the aforementioned three domains. As a result, the second HMlayer adjoins the first domain at front side 30 f, adjoins the seconddomain at a first diagonal side 30 s, and adjoins the fourth domain at asecond diagonal side 30 s. Magnetization 30 m is responsible forpreventing magnetizations 55 m 1, 55 m 2, and 55 m 4 from flipping to adirection that is opposite to the preset direction thereby stabilizingthe second top shield 55, side shield 31, and free layer 3 f in thesecond MR sensor in FIG. 2.

The present disclosure encompasses another embodiment shown in FIG. 5Awhere the HM layer 20 in FIG. 3A is shifted from above a third domain inthe top shield 15 to below the third domain 15 c. In other words, HMlayer 20 has essentially the same trapezoidal shape as the third domain15 c and adjoins a bottom surface thereof such that backside 20 b isbelow top shield backside 15 e, and front side 20 f is about ½ h fromtop shield front side 15 f. It should be understood that the second HMlayer when present may be shifted from above a domain (i.e. third domainin FIG. 3B) to adjoining a bottom surface of the domain.

In FIG. 5B, a cross-sectional view of the HM stabilization schemecorresponding to FIG. 5A in the first read head is shown along a planethat is parallel to the ABS 18-18 and includes front side 20 f of HMlayer 20. The HM layer has down-track thickness t1 less than thicknesst2 of magnetic domains 15 b-15 d, and is formed within an isolationlayer 22 that is behind the junction (side) shield 21 and first MRsensor (layers 2 d, 2 f, 2 h) in FIG. 2.

According to another embodiment depicted in FIG. 6A that represents amodification of the shield stabilization structure shown in FIG. 5A, thetop shield retains the cross-track width w and height h. In this case,the top shield has a first domain 15 a at the ABS with a backside about½ h from the ABS 18-18, and a second domain 15 b adjoining the backsideof the first domain and having a backside 15 e. Both of the domainsshare a first side 15 s 1 and a second side 15 s 2 that are orthogonalto the ABS. A key feature is that the HM layer 20 x has an area boundedby front side 20 f, backside 20 b, and sides 20 s that is enlarged withrespect to HM layer 20 in the previous embodiments. Preferably, HM layer20 x has a height of (½ h+h2) that is greater than h, and a width w2that is larger than w. Note that front side 20 f is maintained at height½ h. However, backside 20 b is now a distance h2>½ h from the front side20 f. In the exemplary embodiment, each side 20 s preferably extends adistance greater than ½ w from first MR sensor 2 in a cross-trackdirection. In other embodiments, HM layer 20 x maintains a width w buthas height (½ h+h2), or HM layer 20 x maintains height h but has widthw2.

Magnetization 15 m 1 in the first top shield domain 15 a is opposite tomagnetization 15 m 2 in the second top shield domain 15 b, andmagnetization 20 m in HM layer 20 x is preferably aligned in the samecross-track direction as 15 m 2 in order to maintain 15 m 1 (and 15 m 2)in their preset directions in a closed loop thereby preventing themagnetizations from flipping to an incorrect state (direction). One ofthe advantages of the so-called “extended” HM layer design in FIG. 6A isto minimize edge magnetostatic coupling that competes with HM layerexchange coupling with the top shield domain 15 b.

The present disclosure also anticipates an embodiment where in additionto the stabilization scheme for top shield 15 shown in FIG. 6A, thesecond top shield 55 may be stabilized by an extended HM layer 30 x asshown in FIG. 6B. HM layer 30 x has a backside 30 b of width w2 betweensides 30 s, front side 30 f that is ½ h from the ABS 18-18, and backside30 b at height h2 (where h2>½ h) from the front side such that the areaof HM layer 30 x is greater than that of (h×w) in the second top shieldfrom a top-down view. Magnetization 55 m 1 in a top shield domain 55 aat the ABS is opposite to magnetization 55 m 2 in a top shield domain 55b with backside 55 e. Magnetization 30 m in HM layer 30 x is preferablyaligned in the same cross-track direction as 55 m 2 in order to maintain55 m 1 (and 55 m 2) in their preset directions, and provide magneticstability to the second top shield during thermal excursions.

As illustrated by the top-down view in FIG. 7, the present disclosurealso encompasses a hard magnet stabilization scheme of a top shield 15 rhaving a substantially ring shape with a center portion that is filledwith an isolation layer 33. The center portion contacts inner side 15 s2 of the ring shape and has a cross-track width (diameter d) at a plane41-41 formed parallel to the ABS and that passes through center point Cof the center portion. The ring shape has a cross-track width r that isa plurality of microns between the outer side 15 s 1 and inner side 15 s2 at plane 41-41. Preferably d is greater than r, but in someembodiments, the relationship r≥d may be acceptable. The ring shaped topshield has a front side 15 f having a cross-track width w at the ABS18-18 and above the first MR sensor 2. Magnetization 15 m 1 forms avortex around the center and thus provides an optimum stable state,which increases stability of reader response. In other embodiments,other closed shapes such as an ellipse, square, rectangle, or polygonmay replace the ring shape. A key feature is that all of the closedshapes have an open center portion and a vortex magnetization around thecenter portion.

In the exemplary embodiment, a HM layer 20 c may be formed on a topsurface, bottom surface, or within a portion of the ring shaped topshield. The HM layer has height h1 between front side 20 f and backside20 e, and width w1 between two sides 20 s. Because of the closed loopmagnetization 15 m 1, the HM layer placement (coupling location) may beanywhere in the ring between the inner side 15 s 2 and outer side 15 s1. The HM shape is not limited to a square, rectangle, or trapezoid.When the HM layer is within a portion of the top shield, the HM layerand top shield magnetizations form a vortex magnetization. In otherembodiments, magnetization 20 m in the HM layer is set in a directionthat aligns with 15 m 1 and thereby maintains the top shieldmagnetization in the preset direction. As shown in FIG. 7, top shield 15r may have a substantially circular shape. Alternatively, the top shieldshape may be an ellipse where the height m between the ABS 18-18 and apoint 15 t on the outer side that is farthest from the ABS is unequal tothe cross-track width (d+2r) between points on the outer side of thering shape on plane 41-41. In other embodiments, the ring shape may beasymmetrical in that the distance between the inner and outer sides isnot constant in regions behind the ABS. For example, distance k2 betweenthe inner side and outer side in a back portion of the ring may beunequal to r in a mid section of the ring at plane 41-41. In someembodiments, the height k1 between front side 15 f and a point on theinner side behind MR sensor 2 is less than k2.

According to one embodiment, the shape of the HM layer 20 c is containedbetween the inner side 15 s 2 and outer side 15 s 1. In otherembodiments, a portion of the HM layer may extend beyond one or bothsides 15 s 1, 15 s 2, as long as magnetization direction 15 m 1 is notdisturbed. Preferably, the front side 20 f is not at the ABS in order tosatisfy a reduced RRS requirement for 2DMR (and 3DMR) designs. In apreferred embodiment, a HM layer is employed to stabilize only the firsttop shield in a 2DMR scheme. For a 3DMR structure, a first HM layer maybe used to stabilize the first top shield while a second HM layerstabilizes a second top shield. In other words, a HM layer is generallynot needed to stabilize the second top shield in a 2DMR structure or athird top shield (not shown) in a 3DMR layout.

In an alternative embodiment for a 2DMR scheme, a second HM layer (20 ccopy not shown) that has substantially the same shape and size as thefirst HM layer 20 c may be used to stabilize a second top shield with aring shape or closed loop shape that supports a vortex magnetization aspreviously described with regard to top shield 15 r. Accordingly, thepresent disclosure anticipates a 2DMR scheme wherein one or both of thetop shield and second top shield are comprised of a ring shape describedherein and are stabilized by a HM layer. In other words, top shield 15in the ABS view of FIG. 2 may be replaced by ring shaped shield 15 r ofthis embodiment, and a second ring shaped shield having essentially thesame structure as shield 15 r may replace second top shield 55.

In another embodiment depicted in FIG. 16, a 3DMR structure isillustrated wherein the 2DMR stack of layers shown in FIG. 2 is modifiedby forming a second isolation layer 75 on the second top shield 55, athird bottom shield 80 on the second isolation layer, a third MR sensorcomprised of bottom layer 4 d, third free layer 4 f, and top layer 4 hon the third bottom shield, and a third top shield 95 on the third MRsensor. A third junction shield 91 having magnetization 91 m is formedadjacent to the third MR sensor and separated therefrom by isolationlayer 88. Preferably, first HM layer 20 (or 20 x or 20 c) is employed tostabilize top shield 15, and second HM layer 30 (or 30 x or 20 c or thelike) is used to stabilize the second top shield 55 since the first andsecond top shields are more susceptible to magnetization flipping thanthe third top shield in a 3DMR design. Nevertheless, in someembodiments, a third HM layer (not shown) formed according to anembodiment of the present disclosure may adjoin a top or bottom surfaceof the third top shield 95, or may be formed within the third top shieldfor stabilization purposes. The third top shield has magnetization 95 m1 aligned in the same direction as magnetization 91 m.

Referring to FIG. 8A, the present disclosure also encompasses a wholeshield coupling design where a HM layer contacts essentially all of atop shield bottom surface except in a region proximate to the sides andbackside of the MR sensor. A top-down view is shown where the top shield15 having width w and height h is removed to reveal the shape of theunderlying HM layer 20. The HM layer has a backside 20 b having width w,and outer sides 20 s 2 each with height h from the ABS 18-18 to the HMlayer backside. There is a junction shield 21 surrounding the MR sensor2 at the ABS and extending a cross-track distance n of a plurality ofhundreds of nm to a plurality of microns on each side of the centerplane 44-44 to an inner side 20 s 1 of the HM layer. Each inner side 20s 1 is aligned orthogonal to the ABS and has a height f (greater thanheight b of the MR sensor) from the ABS to an ABS facing side 20 r ofthe HM layer. Side 20 r has a cross-track width 2 n and is parallel tothe ABS. HM layer magnetization 20 m is parallel to the ABS.

In FIG. 9, an ABS view is shown of a 1DMR scheme where the HM layerstabilization structure from the FIG. 8A layout is applied. Similar tothe POR design in FIG. 1, there is a MR sensor comprised of layers 2 d,2 f, 2 h between top shield 15 and bottom shield 1. Preferably, junctionshield 21 has a single ferromagnetic (FM) layer, or a plurality of FMlayers that are ferromagnetically coupled with each having amagnetization in the (+) y direction, for example. In particular, HMlayer provides more stabilization than achieved previously not only bysupporting a steady magnetization 21 m, but also by preventingmagnetization 15 m 1 from flipping to an opposite direction from thedesired direction that was preset during fabrication. Preferably, aportion of HM layer 20 and the junction shield 21 on each side of centerplane 44-44 have a top surface 20 t, 21 t, respectively, that arecoplanar with the top surface 2 t of the MR sensor. Magnetization 20 mmaintains top shield magnetization 15 m 1 and junction shieldmagnetization 21 m in a positive (y) direction, for example, to providea stable longitudinal bias field to free layer 2 f. In this embodiment,HM layer 20 and the junction shield each have a bottom surface formed onisolation layer 40.

Referring to FIG. 8B, a top-down view is depicted in an alternativeembodiment wherein both of the first top shield 15 and second top shield55 are stabilized by whole shield coupling with a HM layer. In thisembodiment, the second top shield and overlying layers are removed toshow the underlying second HM layer 30 in a 2DMR structure (or in a 3DMRstructure). The second HM layer contacts essentially all of the secondtop shield bottom surface except in a region proximate to the sides andbackside of the second MR sensor. The second HM layer has a backside 30b having width w, and outer sides 30 s 2 that extend from the ABS 18-18to a height h at the second HM layer backside. A second junction shield31 surrounds the second MR sensor 3 at the ABS and extends a cross-trackdistance n on each side of center plane 44-44 to an inner side 30 s 1 ofthe second HM layer. Each inner side 30 s 1 is aligned orthogonal to theABS and has a height f (greater than height b of the second MR sensor)from the ABS to an ABS facing side 30 r of the second HM layer. Side 30r has a cross-track width 2 n and is parallel to the ABS. HM layermagnetization 30 m is parallel to the ABS, and preferably in the samedirection as magnetization 20 m in the first HM layer.

Referring to FIG. 10, an ABS view is shown of a 2DMR scheme where the HMlayer stabilization structure from FIG. 8A is included with the secondHM layer stabilization structure from FIG. 8B. Effectively, the firstembodiment illustrated in FIG. 2 is modified to replace outer portionsof junction shields 21, 31 on each side of center plane 44-44 with HMlayer 20, and 30, respectively. Furthermore, instead of HM coupling to asingle top shield domain in previous embodiments, there is substantiallymore HM coupling with a top shield in this “whole shield coupling”embodiment. Junction shields 21, 31 may be comprised of a singlemagnetic layer. HM layer 20 provides stability to magnetization 21 m andmagnetization 15 m 1 while second HM layer 30 provides stability tomagnetizations 31 m and 55 m 1. Preferably, a portion of HM layer 30 andthe junction shield 31 on each side of center plane 44-44 have topsurfaces 30 t, 31 t, respectively, that are coplanar with the topsurface 3 t of the second MR sensor. Second HM layer 30 has a bottomsurface formed on isolation layer 48.

The present disclosure also encompasses a method of forming a read headstructure wherein a top shield is stabilized by a hard magnet layerdisclosed herein. According to one embodiment shown from the ABS viewsin FIGS. 11-15, a series of steps is provided where a MR sensor withsidewalls is formed on a bottom shield, and then a junction shield isplated or deposited on the MR sensor sidewalls on each side of thecenter plane. A HM layer is deposited with an inner side that adjoinsthe junction shield and has essentially whole shield coupling with anoverlying top shield that is formed in a subsequent step according to anembodiment described previously with regard to FIG. 9.

In FIG. 11, a first step in the fabrication process is depicted whereina bottom shield 1 is formed on a substrate (not shown) by a platingmethod, for example. Thereafter, layers 2 d, 2 f, 2 h in the first MRsensor stack are sequentially formed on a top surface of the bottomshield by a sputter deposition process. According to one embodiment thatrepresents a bottom spin valve configuration, layer 2 d is comprised ofa lower seed layer, a middle antiferromagnetic (AFM) layer, a referencelayer on the AFM layer and an upper non-magnetic spacer on a top surfaceof the reference layer, and layer 2 h is a capping layer formed on freelayer 2 f. The non-magnetic spacer may be Cu in a GMR sensor or one ormore metal oxides in a tunnel barrier layer in a TMR sensor. However,the present disclosure also encompasses other sensor designs thatinclude at least a reference layer, free layer, and non-magnetic spacerbetween the reference layer and free layer wherein the reference layermay be part of layer 2 d in a bottom spin valve configuration, or partof layer 2 h in a well known top spin valve configuration. In a top spinvalve configuration, layer 2 d is a seed layer and layer 2 h iscomprised of a non-magnetic spacer contacting a top surface of freelayer 2 f, and a reference layer and capping layer sequentially formedon the non-magnetic spacer.

During the following step in the fabrication sequence, a photoresistlayer is spin coated on the MR sensor top surface 2 t, and is thenpatternwise exposed and developed by a conventional photolithographyprocess to generate a pattern including a photoresist island 60 having awidth a between sidewalls 60 s in the cross-track direction. Width acorresponds to the desired cross-track width of the sensor top surfacein the completed read head structure. The photoresist pattern typicallyincludes a plurality of islands arranged in rows and columns from atop-down view that is not shown in order to focus on the key features inthe drawing. From a top-down view (not shown), the island has acircular, elliptical, or polygonal shape depending on the desired shapeof the MR sensor. There are openings 70 on either side of thephotoresist island that expose substantial portions of top surface 2 t.A portion of top surface 2 t is also uncovered along a backside (notshown) of the photoresist island such that adjacent islands in thephotoresist pattern are completely separated from each other.

Referring to FIG. 12, a reactive ion etch (RIE) or ion beam etch (IBE)process is performed to transfer the shape of the photoresist island 60through the MR sensor stack of layers. The etch process stops on a topsurface 1 t of the bottom shield. In some embodiments, the resultingsidewalls 2 s are substantially vertical. In other embodiments, ionsfrom the IBE or RIE process may be directed at a non-vertical angle withrespect to top surface 1 t such that a cross-track width of top layer 2h is less than a cross-track width for bottom layer 2 d.

Referring to FIG. 13, an isolation layer 40 that is made of one or morenon-magnetic materials is conformally deposited on top surface 1 t andon sidewalls 2 s by a plasma vapor deposition (PVD) process or the like.The isolation layer may have a lower metal oxide layer and an uppermostmetal layer, for example, where the metal layer is employed to promotethe plating of magnetic layers in subsequent steps. Next, the junctionshield layer 21 is plated or deposited on a top surface 40 s ofisolation layer 40. A chemical mechanical polish (CMP) process may beperformed to remove the photoresist island and provide a top surface 21t on the junction shield that is coplanar with top surface 2 t of the MRsensor.

In FIG. 14, a second photoresist layer 61 is coated on the junctionshield 21 and MR sensor top surface 2 t, and is then patternwise exposedand developed to form sides 61 s that are a cross-track distance n fromcenter plane 44-44. An IBE or IBE step is carried out to remove portionsof the junction shield that are not protected by the second photoresistlayer, and stops on top surface 40 t thereby generating sides 21 s onthe junction shield layer that are coplanar with sides 61 s, and areseparated from the center plane by the cross-track distance n at theABS. Opening 71 is formed adjacent to sides 21 s.

Referring to FIG. 15, HM layer 20 is plated or deposited on exposedportions of top surface 40 t to a level at least up to plane 43-43 thatincludes top surface 2 t of the MR sensor. A second CMP process may beperformed to remove the second photoresist layer and form a top surface20 t on HM layer 20 that is coplanar with top surface 21 t on junctionshield 21, and top surface 2 t on the MR sensor.

Thereafter, top shield 15 is formed on top surfaces 2 t, 20 t, 21 t by aconventional process to yield the read head structure shown in FIG. 9.At this point, an anneal step may be performed to set the magnetizationdirection 15 m 1 in the top shield. Because of ferromagnetic couplingbetween the junction shield 21 and top shield, magnetization 21 t isaligned in the same direction as 15 m 1. Subsequently, a temperaturefrom RT to about 100° C. and an applied field with a magnitude ofthousands of Oe is used to set magnetization 20 m in the HM layer.

For a 2DMR scheme, isolation layer 25 is deposited on top shield 15, andthen the process steps shown in FIGS. 11-15 are repeated to form asecond MR sensor above the first MR sensor that is depicted in FIG. 10.In an alternative embodiment, a second HM layer 30 is omitted such thatonly the second junction shield 31 is employed adjacent to the second MRsensor. Thus, there is no HM layer to stabilize the second top shield 55in the alternative embodiment.

In summary, we have disclosed a stabilized shield structure wherein ajunction shield that provides longitudinal biasing to an adjacent freelayer in a MR sensor is ferromagnetically coupled to a top shield thatis in turn stabilized by a hard magnet layer adjoining a top or bottomsurface of the top shield, or that replaces a magnetic domain in the topshield. Enhanced sensor performance in terms of high output sharpness(higher SNR) and lower BER is achieved with no significant costadditions compared with current fabrication schemes.

While this disclosure has been particularly shown and described withreference to, the preferred embodiment thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade without departing from the spirit and scope of this disclosure.

We claim:
 1. A magnetic read head structure, comprising: (a) a firstmagnetoresistive (MR) sensor formed on a first bottom shield and havinga free layer with a first magnetization in a first direction, the firstMR sensor has sidewalls that extend from a top surface thereof to thefirst bottom shield wherein the top surface has a first cross-trackwidth (a) at an air bearing surface (ABS); (b) a first top shield thatcontacts the first MR sensor top surface and having a second cross-trackwidth (w) at the ABS where w>a, and a backside that is a first height(h) from the ABS, the first top shield has a second magnetization in thefirst direction; (c) a first junction shield on each side of a centerplane that bisects the first MR sensor in a down-track direction, thefirst junction shield is adjacent to the first MR sensor sidewalls, hasan outer side on each side of the center plane at a third cross-trackwidth, and has a third magnetization in the first direction; and (d) afirst hard magnet (HM) layer that contacts essentially all of a bottomsurface of the first top shield except for a portion above the first MRsensor and first junction shield, the first HM layer has a fourthmagnetization that is set or reset to the first direction from roomtemperature to about 100° C., and maintains the second magnetization inthe first direction in the absence of an external magnetic field therebyproviding enhanced stability to the first and third magnetizations, thefirst HM layer has the second cross-track width at a backside thereofthat is at the first height, and has inner sides that adjoin each outerside of the first junction shield.
 2. The magnetic read head structureof claim 1 wherein a top surface of the first HM layer is coplanar witha top surface of the first junction shield.
 3. The magnetic read headstructure of claim 1 wherein the first HM layer is comprised of CoPt,CoCrPt, or FePt.
 4. The magnetic read head structure of claim 1 whereinthe third cross-track width is from a plurality of hundreds of nm to aplurality of microns.
 5. The magnetic read head structure of claim 1further comprising; (a) an isolation layer formed on a top surface ofthe first top shield; (b) a second bottom shield formed on the isolationlayer; (c) a second MR sensor formed on the second bottom shield andhaving a second free layer with a fifth magnetization in the firstdirection, the second MR sensor has sidewalls that extend from a topsurface thereof to the second bottom shield wherein the second MR sensortop surface has the first cross-track width at the ABS; (d) a second topshield that contacts the second MR sensor top surface and has the secondcross-track width at the ABS, and a backside that is at the first heightfrom the ABS, the second top shield has a sixth magnetization in thefirst direction; (e) a second junction shield that is adjacent to thesecond MR sensor sidewalls and with an outer side on each side of thecenter plane at the third cross-track width, the second junction shieldhas a seventh magnetization in the first direction; and (f) a second HMlayer that contacts essentially all of a bottom surface of the secondtop shield except for a portion above the second MR sensor and secondjunction shield, the second HM layer has an eighth magnetization that isset or reset to the first direction from room temperature to about 100°C., and thereby maintains the fifth, sixth, and seventh magnetizationsin the first direction in the absence of an external magnetic field, thesecond HM layer has the second cross-track width at a backside thereofthat is at the first height, and has inner sides that adjoin each outerside of the second junction shield.